Pleated Filter Material for Smoking Articles

ABSTRACT

A filter material for manufacturing a segment of a smoking article is described, wherein the filter material comprises a hydro-entangled nonwoven and the nonwoven comprises fibers, wherein the fibers are selected from the group consisting of pulp fibers, fibers of regenerated cellulose and mixtures thereof, and these fibers are together contained in the nonwoven in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven, and wherein the nonwoven is in the form of a web, has a longitudinal direction in the running direction of the web, a cross direction orthogonal thereto and lying in the plane of the web and a thickness direction orthogonal to longitudinal direction and the cross direction. The nonwoven is shaped such that it has a wave structure in the plane formed by the cross direction and the thickness direction with a wave height of at least 50 µm and at most 1000 µm, as well as a wave length ( 22 ,  32 ,  42 ) of at least 150 µm and at most 5000 µm.

FIELD OF INVENTION

The invention relates to a filter material suitable for the manufacture of a segment in a smoking article, which is pleated and from which segments for smoking articles can be manufactured in an efficient manner. The invention also relates to a segment for a smoking article, manufactured from this filter material.

BACKGROUND AND PRIOR ART

Smoking articles are typically rod-shaped articles, which consist of at least two rod-shaped segments disposed next to each other. One segment contains a material which is capable of forming an aerosol upon heating and at least one further segment serves to influence the properties of the aerosol.

The smoking article can be a filter cigarette, in which a first segment contains the aerosol-forming material, in particular tobacco, and a further segment is designed as a filter and acts to filter the aerosol. In this regard, the aerosol is generated by combustion of the aerosol-forming material and the filter primarily serves to filter the aerosol and to provide the filter cigarette with a defined draw resistance.

The smoking article, however, can also be what is known as a heated tobacco product, wherein the aerosol-forming material is only heated but not combusted. This means that the number and amount of substances in the aerosol which are damaging to health are reduced. Such a smoking article also consists of at least two, more often, however, of more, in particular of four segments. One segment contains the aerosol-forming material, which typically comprises tobacco, reconstituted tobacco or tobacco prepared by other processes. Further, optional segments in the smoking article sometimes serve to transfer the aerosol, to cool the aerosol or to filter the aerosol.

The segments are usually wrapped with a wrapper material. Very often, paper is used as wrapper material.

Unless it is explicitly stated below or is directly clear from the context, the “segment” should be understood to refer to the segment of a smoking article that does not contain the aerosol-forming material, but rather serves, for example, to transfer, cool or filter the aerosol.

In the prior art, it is known to form such segments from polymers such as cellulose acetate or polylactides. After consumption of the smoking article, the smoking article has to be disposed of in a suitable manner. In many cases, however, the consumer simply disposes of the consumed smoking article in the environment, and attempts to restrict this behavior by information or fines have had little success.

Because cellulose acetate and polylactides biodegrade only very slowly in the environment, paper and cellulose-based nonwovens have increased in importance. During the manufacture of a segment, a web of paper or of a cellulose-based nonwoven is initially pleated in longitudinal direction, then formed into a continuous rod and wrapped with a wrapper material. Then the continuous rod is cut into pieces suitable for further processing.

During pleating, the web runs through two rollers provided with a pattern, which emboss this pattern onto the web under high pressure. Typically, this pattern is a line pattern oriented in the running direction of the web. The embossed lines weaken the web in the direction orthogonal to the running direction, the cross direction, so that then a continuous rod can be formed more easily by gathering the web in cross direction.

During pleating, however, it can happen that due to the significant pressure of the rollers, the web is cut in the longitudinal direction und tears during further processing or causes other technical problems. Thus, there is a need for a filter material that does not have this disadvantage or only to a lesser extent, but otherwise is as identical as possible to other known filter materials.

In DE 10 2005 017 478 A1, a tobacco smoke filter is described that contains fibers from regenerated cellulose (e.g. Lyocell) and to which an adsorbent has been added. More than one adsorbent is added to the fibers of the tobacco smoke filter and/or the tobacco smoke filter contains the adsorbent between the fibers. That document describes that with such a tobacco smoke filter, a high loading of adsorbent can be obtained. In one embodiment, nonwovens were manufactured from loaded Lyocell staple fibers. One nonwoven received a loading of 50% by weight of “Siralox 40” (Sasol Ltd.) into the Lyocell fibers used for its manufacture. The other nonwoven received a loading of 50% by weight of HY-Zeolite in its fibers. After adding activated carbon granules to one of the two nonwoven layers, the two layers were connected to each other by needling.

SUMMARY OF THE INVENTION

An objective of the invention is to provide a filter material for a smoking article that can be processed into a segment of a smoking article with high productivity and otherwise is as similar as possible to conventional filter materials with respect to its properties.

This objective is achieved by means of a filter material as claimed in claim 1, a segment of a smoking article as claimed in claim 17, and a smoking article as claimed in claim 24, as well as by a process for manufacturing the filter material according to the invention as claimed in claim 27. Advantageous embodiments are provided in the dependent claims.

The inventors have found that this objective can be achieved by means of a filter material for manufacturing a segment for a smoking article, wherein the filter material comprises a hydro-entangled nonwoven, and the nonwoven comprises fibers, wherein the fibers are selected from the group consisting of pulp fibers, fibers from regenerated cellulose and mixtures thereof and these fibers are together contained in the nonwoven in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven and wherein the nonwoven is web-shaped, has a longitudinal direction in the running direction of the web, a cross direction orthogonal thereto lying in the web plane and a thickness direction orthogonal to the longitudinal direction and the cross direction and is shaped such that the nonwoven has a wave structure in the plane formed by the cross direction and the thickness direction with a wave height of at least 50 µm and at most 1000 µm, as well as a wave length of at least 150 µm and at most 5000 µm.

Although the term “hydro-entangled” at first indicates the underlying manufacturing process, it has to be considered that a hydro-entangled nonwoven has characteristic structural properties, which differentiate it from other nonwovens and which, according to the knowledge of the inventors, cannot be obtained in an identical manner by other manufacturing processes. Other than for paper, for example, wherein the strength is primarily caused by hydrogen bonds and the fibers are mainly disposed in the plane of the paper, the strength of the hydro-entangled nonwoven is obtained by entanglement of the fibers and thus a significant proportion of the fibers are also oriented in the thickness direction of the nonwoven.

During manufacture of the hydro-entangled nonwoven according to the invention, the fibers are deposited on a water-permeable wire and are consolidated by a plurality of water jets disposed in cross direction and directed onto the fibers. Due to the special choice of the arrangement and the properties of the water jets, a wave structure can be generated according to the invention in cross direction that is similar to a structure that can also be obtained by pleating. The nonwoven and the filter material according to the invention comprising the nonwoven are thus pre-pleated.

During the manufacture of a continuous rod from the filter material according to the invention, the filter material runs through two rollers provided with a pattern. Because the filter material according to the invention has already been pre-pleated, all that is required is a substantially lower pressure in order to obtain sufficient pleating of the filter material, or the pleating can even be entirely dispensed with. In this manner, the possibility of accidentally cutting the filter material in the longitudinal direction can be substantially reduced. In this manner, the number of interruptions during manufacture of the continuous rod and the segments can be reduced and the productivity can be increased, which represents a substantial advantage of the filter material according to the invention.

The nonwoven is web-shaped and has a longitudinal direction in the running direction of the web, as well as a direction orthogonal thereto and lying in the web plane, which is termed the cross direction. The direction orthogonal to the longitudinal direction and cross direction is termed the thickness direction. The nonwoven contained in the filter material according to the invention has a wave structure in the plane formed by the cross direction and the thickness direction, the cross-sectional area, wherein the wave length extends substantially in cross direction and the wave height substantially in the thickness direction. According to the invention, the wave height is at least 50 µm and at most 1000 µm, preferably at least 100 µm and at most 900 µm and particularly preferably at least 150 µm and at most 800 µm. According to the invention, the wave length is at least 150 µm and at most 5000 µm, preferably at least 300 µm and at most 4000 µm and particularly preferably at least 500 µm and at most 2000 µm.

The shape of the wave structure is not of particular importance, but is has to be sufficiently strongly pronounced for gathering of the nonwoven in cross direction to be carried out more easily than for the same nonwoven without a wave structure. Due to the manufacturing process, the wave height and wave length can also vary substantially within a cross sectional area. This is not of importance for the effect according to the invention, as long as the wave length and the wave height are within the indicated ranges over the majority of the cross-sectional area, in particular over at least 60%, preferably at least 75% of the cross-sectional area.

The wave structure also does not have to be pronounced on the upper side and the lower side of the nonwoven; it is sufficient for it to be pronounced on one side because the thin areas created thereby in the wave valleys facilitate gathering of the nonwoven in cross direction and thus reduce the pressure required for pleating during manufacture of the segment.

The roughness of the surface alone is in general not sufficient to achieve the effect according to the invention.

The wave structure of the nonwoven can be determined by embedding a sample of the nonwoven in a suitable epoxy resin. After curing the epoxy resin, the sample can be ground or cut by a microtome in the cross-sectional plane of the nonwoven so that the cross-sectional area is visible under an optical microscope. With an optical microscope, the wave structure can be made visible, and the wave height and wave length can be measured. A camera connected to the optical microscope can serve to record images of sections of the cross-sectional area.

The conditions indicated regarding wave height and wave length are sufficiently fulfilled for the invention, when they are fulfilled in representative sections of a cross-sectional area. Due to the manufacturing process, the wave structure will in general change only insignificantly over the longitudinal direction of the nonwoven, and so in order to test the requirements for wave height and wave length, it is not necessary to carry out such a measurement in the longitudinal direction on several cross-sectional areas.

As an alternative to an optical microscope, a scanning electron microscope can also be used.

For a good tensile strength and for adjustment of the draw resistance or the filtration efficiency of a segment manufactured from the filter material according to the invention, the hydro-entangled nonwoven contains pulp fibers, fibers from regenerated cellulose or a mixture thereof in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven. Preferably, the amount of fibers is at least 60% and at most 95% respectively with respect to the mass of the hydro-entangled nonwoven.

The pulp fibers can preferably be sourced from coniferous wood, deciduous wood or other plants such as hemp, flax, jute, ramie, kenaf, kapok, coconut, abacá, sisal, cotton or esparto grass. Mixtures of pulp fibers of different origin can also be used. Particularly preferably, the pulp fibers are sourced from coniferous wood, for example, spruce, pine or fir, because these fibers, due to their length, result in good strength in the hydro-entangled nonwoven. Pulp sourced from coniferous wood, which is known as reinforced pulp, which produces a particularly high strength, and mercerized pulp, which produces a particularly high thickness and low density, are more particularly preferred.

The pulp fibers can be bleached or unbleached. Due to their white color, bleached pulp fibers offer advantages for the appearance of a segment manufactured from the filter material according to the invention, while unbleached pulp fibers, which then have a light brown to a dark brown color, are more environmentally friendly because the bleaching process can be dispensed with. Mixtures of bleached and unbleached pulp fibers can also be used for better adjustment of the color of the filter material according to the invention.

The fibers from regenerated cellulose are preferably viscose fibers, Modal fibers, Lyocell®, Tencel® or mixtures thereof. These fibers have a good biological degradability and can be used to optimize the strength, thickness or density of the hydro-entangled nonwoven and to adapt the filtration efficiency of the segment manufactured therefrom for the smoking article.

In a more particularly preferred embodiment, the filter material according to the invention comprises a hydro-entangled nonwoven, which substantially exclusively, but at least to 95% with respect to the mass of the hydro-entangled nonwoven, consists of pulp fibers, fibers from regenerated cellulose or a mixture thereof. This more particularly preferred embodiment allows for a very good biological degradability and a quick degradation by contact with water and simultaneously a very low impact on the taste of the smoking article manufactured from the filter material.

In a preferred embodiment of the filter material according to the invention, the hydro-entangled nonwoven contains at least 5% and less than 50%, particularly preferably less than 40% and more particularly preferably less than 30% staple fibers of cellulose acetate, wherein the percentages are with respect to the mass of the hydro-entangled nonwoven.

Additives such as alkenyl ketene dimers (AKD), alkenyl succinic acid anhydride (ASA), fatty acids, starch, starch derivatives, carboxymethyl cellulose, alginates or substances to adjust the pH, for example organic or inorganic acids or salts thereof or bases, can be added to adjust specific properties of the nonwoven. The skilled person is able to determine the type and amount of such additives from experience.

The basis weight of the hydro-entangled nonwoven is preferably at least 25 g/m² and at most 150 g/m², particularly preferably at least 35 g/m² and at most 120 g/m² and more particularly preferably at least 40 g/m² and at most 100 g/m². The basis weight influences the tensile strength of the hydro-entangled nonwoven, wherein a higher basis weight can lead to a higher tensile strength.

The thickness of the hydro-entangled nonwoven is preferably at least 100 µm and at most 1000 µm, particularly preferably at least 120 µm and at most 800 µm and more particularly preferably at least 150 µm and at most 750 µm. The thickness influences the amount of filter material that can be packed into the segment of the smoking article and therefore the draw resistance and filtration efficiency of the segment, but also the processability of the filter material, because a large thickness can make pleating of the filter material more difficult. The filter material according to the invention enables the thickness to be greater due to the wave structure of the nonwoven without giving rise to problems during pleating. Thus, a filter material according to the invention can be utilized particularly well if segments with high density and high draw resistance are to be manufactured. The measurement of thickness is influenced by the wave structure of the material. For the determination of the thickness, however, this fact is ignored, because the thickness measured in this way can also serve as a measure of how much filter material can be wound on a reel with a given diameter. The thickness can be measured in accordance with EDANA Standard Procedure NWSP 120.6.Ro (15).

The density of the hydro-entangled nonwoven can be obtained by dividing the basis weight by the thickness. The density of the hydro-entangled nonwoven is preferably at least 50 kg/m³ and at most 300 kg/m³, particularly preferably at least 70 kg/m³ and at most 250 kg/m² and more particularly preferably at least 80 kg/m³ and at most 220 kg/m³. These values are with respect to the density before a segment of a smoking article has been manufactured from the filter material according to the invention that comprises this hydro-entangled nonwoven. The density of the hydro-entangled nonwoven determines, among others, the draw resistance and the filtration efficiency of a segment of a smoking article manufactured therefrom. The preferred ranges allow for a good combination of draw resistance and filtration efficiency.

The mechanical properties of the hydro-entangled nonwoven are of importance for the processability of the filter material according to the invention for a segment of a smoking article. The width-related tensile strength of the hydro-entangled nonwoven is preferably at least 0.05 kN/m and at most 5 kN/m, particularly preferably at least 0.07 kN/m and at most 4 kN/m.

The elongation at break of the hydro-entangled nonwoven is of importance because, when processing the filter material according to the invention to produce a segment of a smoking article, the filter material is being pleated and therein a particularly high elongation at break is of advantage. In this regard, the wave structure of the nonwoven allows for a particularly high elongation at break in cross direction and facilitates pleating during manufacture of the segment. The elongation at break in cross direction of the hydro-entangled nonwoven is preferably at least 1% and at most 50% and particularly preferably at least 3% and at most 40%.

Tensile strength and elongation at break can depend on the direction in which the sample for the measurement is taken from the hydro-entangled nonwoven. The requirements regarding the tensile strength of the hydro-entangled nonwoven are fulfilled if the tensile strength in at least one direction is within the indicated, preferred or particularly preferred ranges. The elongation at break is indicated and is to be measured in cross direction.

The filter material according to the invention comprises the hydro-entangled nonwoven. Preferably, however, the hydro-entangled nonwoven according to the invention makes up the predominant majority of the filter material, so that preferably, at least 80% of the mass of the filter material is formed by the hydro-entangled nonwoven and particularly preferably, at least 90% of the mass of the filter material is formed by the hydro-entangled nonwoven.

Apart from the hydro-entangled nonwoven, the filter material according to the invention can comprise further components which, for example influence the processability of the filter material or the properties of a segment manufactured therefrom or the taste of the smoking article. This includes, for example, an impregnation of the nonwoven with flavors, carriers of flavors, in particular filaments impregnated with flavors or substances to increase the stiffness of the filter material or materials which increase the hardness of filters manufactured from the filter material.

In a preferred embodiment of the filter material according to the invention, the filter material comprises the hydro-entangled nonwoven and one or more substances selected from the group consisting of triacetin, glycol, propylene glycol, sorbitol, glycerol, polyethylene glycol, polyvinyl alcohol and triethyl citrate, or mixtures thereof. These substances can assist in improving the adjustment of the filtration efficiency to that of cellulose acetate.

If at least 90% of the mass of the filter material is formed by the hydro-entangled nonwoven, the fulfillment of the aforementioned features of the hydro-entangled nonwoven, for example, with respect to the content of pulp fibers, the content of fibers from regenerated cellulose, the density, the thickness, the basis weight, the tensile strength and the elongation at break can also be tested on the filter material itself, without having to isolate the hydro-entangled nonwoven from the filter material. The aforementioned ranges according to the invention and preferred, particularly preferred, and more particularly preferred ranges and properties are then also valid for the filter material manufactured from the hydro-entangled nonwoven.

Segments for smoking articles according to the invention can be manufactured from the filter material according to the invention using processes that are known in the art. These processes, for example, comprise pleating the filter material, forming a continuous rod from the pleated filter material, wrapping the continuous rod with a wrapper material and cutting the wrapped rod into individual rods of defined length. In many cases, the length of such a rod is an integer multiple of the length of the segments that will then be used in the smoking article according to the invention, and for that reason the rods are cut into segments of the desired length before or during manufacture of the smoking article.

The segment for smoking articles according to the invention comprises the filter material according to the invention and a wrapper material.

In a preferred embodiment of the segment according to the invention, the segment is cylindrical with a diameter of at least 3 mm and at most 10 mm, particularly preferably of at least 4 mm and at most 9 mm and more particularly preferably of at least 5 mm and at most 8 mm. These diameters are particularly advantageous for the use of the segment according to the invention in smoking articles.

In a preferred embodiment of the segment according to the invention, the segment has a length of at least 4 mm and at most 40 mm, particularly preferably of at least 6 mm and at most 35 mm and more particularly preferably of at least 10 mm and at most 28 mm.

The draw resistance of the segment determines, among others, which pressure difference the smoker needs to apply during consumption of the smoking article in order to generate a certain volumetric flow through the smoking article, and it therefore substantially influences the acceptance of the smoking article by the smoker. The draw resistance of the segment can be measured in accordance with ISO 6565:2015 and is given in mm water gauge (mmWG). To a very good approximation, the draw resistance of the segment is proportional to the length of the segment, so that the measurement of the draw resistance can also be carried out on rods that differ from the segment only with respect to their length. The draw resistance of the segment can easily be calculated from this.

The draw resistance of the segment per unit length of the segment is preferably at least 1 mmWG/mm and at most 12 mmWG/mm and particularly preferably at least 2 mmWG/mm and at most 10 mmWG/mm.

The wrapper material of the segment according to the invention is preferably a paper or a foil.

The wrapper material of the segment according to the invention preferably has a basis weight of at least 20 g/m² and at most 150 g/m², particularly preferably of at least 30 g/m² and at most 130 g/m². A wrapper material with this preferred or particularly preferred basis weight provides a particularly advantageous hardness to the segment according to the invention wrapped therewith. This avoids the possibility of the smoker accidentally crushing the segment in the smoking article.

In a preferred embodiment, the segment according to the invention additionally contains at least one capsule that contains flavors. The capsule is often designed so that the smoker can break it by pressure with the fingers and thereby release the flavors so that they can change the taste of the smoking article.

Smoking articles according to the invention can be manufactured according to processes known in the art from the segment according to the invention.

The smoking article according to the invention comprises a segment that contains an aerosol-forming material and a segment that comprises the filter material according to the invention and a wrapper material.

In a preferred embodiment, the smoking article is a filter cigarette and the aerosol-forming material is tobacco.

In a preferred embodiment, the smoking article is a smoking article during the intended use of which the aerosol-forming material is just heated, but not burnt.

The hydro-entangled nonwoven for the filter material according to the invention can be manufactured according to the following process according to the invention, which comprises the following steps A to D.

-   A - providing a fiber web comprising fibers selected from the group     consisting of pulp fibers, fibers from regenerated cellulose and     mixtures thereof, -   B - hydro-entangling the fiber web by means of a plurality of water     jets directed onto the fiber web, -   C - generating a wave structure in the nonwoven by means of a     plurality of water jets directed onto the fiber web, -   D - drying the hydro-entangled nonwoven,

wherein the proportion of said fibers in the fiber web of step A is selected such that these fibers overall are contained in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven in the dried state of step D, wherein the fiber web provided in step A has a longitudinal direction in the running direction of the fiber web, a cross direction orthogonal thereto lying in the plane of the fiber web and a thickness direction orthogonal to the longitudinal direction and cross direction, and the water jets directed onto the fiber web in step C are disposed such that they are at a distance in cross direction from each other from center point to center point of the water jets at the location of the impact onto the fiber web of at least 150 µm and at most 5000 µm and the pressure of each water jet in step C is at least 2 MPa and at most 70 MPa, and the nonwoven obtained in step D has a wave structure in the plane formed by the cross direction and the thickness direction with a wave height of at least 50 µm and at most 1000 µm, as well as a wave length of at least 150 µm and at most 5000 µm. Herein and in the remainder of the disclosure, the “pressure of a water jet” is, as is usual, the pressure in a pressure chamber used to generate the water jet.

According to the findings of the inventors, a water jet with sufficiently high pressure is suitable for the generation of an indentation in the nonwoven running under the water jet, which can be perceived as a wave valley in the cross-sectional area. In this regard, a pressure of at least 2 MPa is required, wherein the pressure, however, very substantially depends on the speed at which the fiber web runs through the machine. A higher pressure is required at higher speeds. At this correspondingly high pressure, the fibers are not only entangled, but are also partially displaced, which substantially contributes to the formation of the wave structure. During the treatment with water jets, the fiber web is typically supported by a wire and also the structure of the wire should preferably be selected so as to be suitable for the intended wave structure, because the fibers are primarily displaced to where the wire is permeable.

In the prior art, during hydro-entangling of a nonwoven, the water jets are not disposed in defined positions with respect to the fiber web, but rather such that a uniform entangling can be achieved by the water jets over the entire area of the running fiber web. This, however, does not result in a wave structure as is characteristic for the filter material according to the invention, even if the pressure of the water jets exceeds 2 MPa.

According to the invention, the water jets, which should serve to generate the wave structure, therefore have to be disposed accordingly, in particular such that water jets with high pressure are not directed onto areas of the fiber web where wave crests should be produced. The water jets which should serve to generate the wave structure in step C are therefore offset in cross direction and are at a distance in cross direction from each other from center point to center point of the water jets at the location of their impact onto the fiber web of at least 150 µm and at most 5000 µm. The water jets can be disposed arbitrarily in the longitudinal direction.

To carry out step B or C, it is also possible to direct the water jets onto both sides of the fiber web. Preferably, the water jets in step C are disposed such that they hit those areas which, when viewed from the respective side, should form the wave valleys.

The pressure of the water jets that serve to entangle the nonwoven in step B can also exceed 2 MPa and, particularly at higher speeds of the fiber web, can be selected so as to be substantially higher. According to the invention, the only important factor is that the effect of all the water jets together over the area of the fiber web is not so uniformly distributed that no wave structure can be generated.

According to the invention, a water jet for generating the wave structure in step C requires a pressure of at least 2 MPa and at most 70 MPa. According to the findings of the inventors, at a pressure of less than 2 MPa, no pronounced wave structure can be generated and at a pressure of more than 70 MPa, even at higher speeds, there is a risk of cutting up the fiber web. Preferably the pressure of the water jets in step C is at least 3 MPa and at most 40 MPa. The pressure for generating the wave structure can be selected as a function of the speed of the fiber web, so that preferably the ratio p/v of the pressure p in MPa to the speed v of the fiber web in m/s is selected such that 2.5 ≤ p/v ≤ 20 and particularly preferably 3 ≤ p/v ≤ 15.

Preferably, the water jets in step C exit through an opening which has an area of at least 450 µm² and at most 50000 µm² and which is particularly preferably a circular opening.

The pressure of the water jets in step B is preferably at least 0.5 MPa and at most 60 MPa, particularly preferably at least 1 MPa and at most 50 MPa, wherein a high pressure should primarily be combined with high speeds of the fiber web in order to avoid cutting up the fiber web. The pressure for entangling the fiber web can be selected as a function of the speed of the fiber web, so that preferably, the ratio p/v of the pressure p in MPa to the speed v in m/s is selected such that 2 ≤ p/v ≤ 10 and particularly preferably 4 ≤ p/v ≤ 8.

The wave structure is characterized by the wave height and wave length can be detected in the cross-sectional area of the nonwoven. According to the invention, the wave height after step D is at least 50 µm and at most 1000 µm, preferably at least 100 µm and at most 900 µm and particularly preferably at least 150 µm and at most 800 µm. According to the invention the wave length after step D is at least 150 µm and at most 5000 µm, preferably at least 300 µm and at most 4000 µm and particularly preferably at least 500 µm and at most 2000 µm.

The hydro-entangled nonwoven manufactured according to this process should be suitable for use in the aforementioned filter material. This means that in particular, it can have all of the features which are described above individually or in combination in connection with the hydro-entangled nonwoven as a component of the filter material and which are defined in the claims directed to the filter material.

The fiber web in step A can be provided using various processes, for example by a wet-laid process or an air-laid process.

In a preferred variation A1 of the process according to the invention, the fiber web in step A is provided by means of a wet-laid process comprising the sub-steps A1.1 to A1.3, A1.1 - manufacturing an aqueous suspension comprising fibers selected from the group consisting of pulp fibers, fibers of regenerated cellulose and mixtures thereof, wherein the amount of these fibers is selected such that these fibers are together contained in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven in the dried state of step D,

-   A1.2 - applying the suspension from step A1.1 to a running wire, -   A1.3 - de-watering the suspension through the running wire in order     to form a fiber web, -   and particularly preferably comprising a further sub-step A1.4, -   A1.4 - adjusting the moisture content of the fiber web by drying or     moistening.

In a preferred embodiment, of the variation A1 of the process according to the invention, the aqueous suspension in step A1.1 has a solid content of at least 0.005% and at most 3.0%, particularly preferably at least 0.005% and at most 1.0%, more particularly preferably at least 0.01% and at most 0.2% and in particular at least 0.01% and at most 0.05%. The particularly low solid content of the suspension enables a fiber web of even lower density to be formed in step A1.3.

In a preferred embodiment, of variation A1 of the process according to the invention, the running wire of steps A1.2 and A1.3 is inclined in the longitudinal direction of the fiber web upwards with respect to the horizontal by an angle of at least 3° and at most 40°, particularly preferably by an angle of at least 5° and at most 30° and more particularly preferably by an angle of at least 15° and at most 25°.

In a preferred embodiment, of variation A1 of the process according to the invention, the de-watering in step A1.3 is supported by generating a pressure difference between the two sides of the running wire, wherein particularly preferably, the pressure difference is generated by vacuum boxes or suitably shaped vanes.

In a preferred embodiment, of variation A1 of the process according to the invention, the drying in step A1.4 is carried out by means of heated drying cylinders or by hot air and moistening by means of a spraying bar. The drying process or the moistening serves to optimally adjust the moisture content of the fiber web for the hydro-entangling in step B. In particular, in step A1.4 the fiber web can at first be dried approximately to the equilibrium moisture content at normal room temperature and relative humidity, then the fiber web is rolled up, transported to a separate device which carries out the hydro-entangling, there it is unrolled and the moisture content is adjusted for the subsequent step B with a spraying bar.

In a preferred variation A2 of the process according to the invention, the fiber web in step A is provided by means of an air-laid process comprising the steps A2.1 and A2.2,

-   A2.1 - manufacturing a fiber web by an air-laid process, wherein the     fiber web comprises fibers that are selected from the group     consisting of pulp fibers, fibers of regenerated cellulose and     mixtures thereof, wherein the amount of these fibers is selected     such that these fibers are together contained in an amount of at     least 50% and at most 100% of the mass of the hydro-entangled     nonwoven in the dried state of step D, and -   A2.2 - moistening the fiber web.

Such an air-laid process of variation A2 can have advantage, because, for example, the energy-intensive drying in step A1.4 of variation A1 can be dispensed with.

In a preferred embodiment, of the process according to the invention, the drying in step D is carried out at least partially by contact with hot air, by means of infra-red radiation or by microwave radiation. In a more particularly preferred embodiment of the process according to the invention, the drying in step D is carried out by through air-drying. By this through-air drying, also called TAD in the specialist field, the fiber material is dried by forcing a warm gas flow, in particular an air flow, through the fiber material. With this through-air drying, the best quality of the hydro-entangled nonwoven can be obtained. Drying by direct contact with a heated surface is also possible, but is less preferred because in that way, the wave structure of the hydro-entangled nonwoven could be destroyed.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a device with which the process according to the invention for manufacturing the hydro-entangled nonwoven can be carried out.

FIG. 2 shows, as an example, the determination of wave height and wave length of the wave structure of the nonwoven.

FIG. 3 shows the cross-sectional area of the nonwoven for a filter material according to the invention.

FIG. 4 shows the cross-sectional area of a filter material not according to the invention after pleating.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some preferred embodiments of the filter material and the process for manufacturing the hydro-entangled nonwoven are described below.

In order to manufacture the hydro-entangled nonwoven that is contained in the filter material according to the invention, the process described below was used, in which the device schematically shown in FIG. 1 has been used.

An aqueous suspension 1 of pulp fibers and fibers of regenerated cellulose was pumped from a storage tank 2 to a running wire 3, inclined upwards against the horizontal, and de-watered by vacuum boxes 9, so that a fiber web 4 was formed on the wire, the general direction of movement of which is indicated by arrow 10. The fiber web 4 was removed from the wire 3 and transferred to a support wire 5, which was also running. If needed, this transfer can be facilitated by a pick-up roll or by entangling the fiber web with water jets before the transfer. On the support wire 5, water jets 11 from devices 6 disposed in three rows in cross direction relative to the fiber web 4 were directed onto the fiber web 4 in order to entangle the fibers and to consolidate the fiber web 4 to form a nonwoven. In a further step, water jets 12 with a higher pressure were also directed onto the fiber web 4 by means of additional devices 7 in order to generate the aforementioned wave structure. In contrast to the devices 6, the devices 7 were set so that the water jets 12 of both rows, in succession in the longitudinal direction, were as far as possible directed to the same position in cross direction. Thus, the water jets 12 of the second row, viewed in the longitudinal direction, were directed onto the wave valleys generated by the water jets 12 of the first row and thus intensified the wave structure generated by the first row. Optional devices 6 a could direct further water jets 11 a onto the fiber web, wherein these water jets, as a function of the arrangement and the pressure could serve for both entangling the nonwoven as well as generating or intensifying the wave structure. In contrast to the representation in FIG. 1 , the water jets of devices 6 a could also be directed onto the fiber web 4 from the same side as the water jets 11 or 12. Then the still moist nonwoven ran through a through-air drier 8 and was dried there.

To manufacture the hydro-entangled nonwoven, a mixture of 80% by weight pulp fibers and 20% by weight Lyocell® fibers was used. The entangling of the fibers was carried out by three rows of water jets 11, which were generated with a pressure of 3 MPa, 5 MPa and 6 MPa with respect to the running direction. The wave structure of the nonwoven was produced by two rows of water jets 12, which were generated with a pressure of 8.5 MPa in both rows. The devices 7 for generating the water jets 12 in both rows were each separated in cross direction by a distance of 2000 µm and had a diameter of 100 µm. The speed of the fiber web was 50 m/min, which is relatively low.

At higher speeds, the pressures of the water jets 11 and 12 have to be correspondingly increased. For the ratio p/v of the pressure p of the water jets for entangling the fiber web in MPa to the speed v of the fiber web in m/s, values of 3/(50/60) = 3.6 to 6/(50/60) = 7.2 were obtained. To generate the wave structure the ratio p/v of the pressure p of the water jets to the speed of the fiber web in m/s was 8.5/(50/60)) = 10.2.

For the nonwoven produced thereby, the basis weight was determined to be 49.6 g/m², the thickness in accordance with NWSP 120.6.Ro (15) was 522 µm and the density was 95 kg/m³. The tensile strength in the longitudinal direction was 8.6 N/15 mm, the elongation at break in cross direction was 31%.

A sample of the nonwoven was embedded in epoxy resin and, after curing the epoxy resin, the sample was cut with a microtome, so that the cross-sectional plane formed by the cross direction and the thickness direction was visible in an optical microscope. With the optical microscope, an image of the cross section was recorded and the wave structure was measured with respect to wave height and wave length.

FIG. 2 shows, as an example, the determination of wave height and wave length of the wave structure of the nonwoven. If the nonwoven 20 has a pronounced wave structure on both sides, then the wave height 21 is determined by the distance in the thickness direction 41 between the highest point of the wave crest 23 and the lowest point of the neighboring wave valley 23 on the same side. The wave length 22 is the distance in cross direction 40 between two points of equal phase angle of the wave structure, here, as an example, shown as the distance between two neighboring wave crests 24 and 25. If the nonwoven 30 has a pronounced wave structure on only one side, the wave height 31 is determined in the same way as the distance in the thickness direction 41 between the highest point of the wave crest 34 and the lowest point of the neighboring wave valley 33 on the same side. The wave length 32 is the distance in cross direction 40 between two points of the same phase angle of the wave structure, here, by way of example, shown as the distance between two neighboring wave crests 34 and 35. The wave height or the wave length can be determined as a single value or as mean value of several measurements, for example three.

FIG. 3 shows the acquired image of the cross-sectional area of the manufactured nonwoven under an optical microscope. A wave structure is clearly discernible and the wave height 41 was determined to be 220 µm and the wave length 42 was 2030 µm.

The nonwoven was used as a filter material according to the invention without adding further components and a segment of a smoking article was manufactured therefrom wrapped with a wrapper paper with a basis weight of 78 g/m². The manufacture of the segment was possible without any problems; in particular, pleating could be carried out with substantially reduced pressure. In further experiments, it was found that pleating could also be dispensed with entirely without having to reduce the production speed or without substantially changing the properties of the segment.

For comparison, FIG. 4 shows a filter material not according to the invention, consisting of a paper made from 100% pulp fibers, that is, not of a hydro-entangled material, after it has been pleated by mechanical pressure between two rolls during manufacture of a segment for a smoking article, but before a segment has been manufactured from it. In addition, a cross-sectional sample was analyzed with an optical microscope and the wave height and wave length were measured using this filter material.

From FIG. 4 , a similar wave structure can be seen and here too, the wave height 51 was determined to be 390 µm and the wave length 52 was 2000 µm. It can be seen that the wave structure of the filter material according to the invention is similar to that of a filter material not according to the invention after pleating, so that pleating of the filter material according to the invention can be carried out with substantially less pressure or can be dispensed with entirely.

These experiments show that the filter material according to the invention, in comparison to filter materials known in the prior art, can facilitate or entirely avoid the pleating step during manufacture of a segment for smoking articles and thus simplify the manufacturing process and reduce the susceptibility to error. 

1. A filter material for manufacturing a segment of a smoking article, wherein the filter material comprises a hydro-entangled nonwoven and the nonwoven comprises fibers, wherein the fibers are selected from the group consisting of pulp fibers, fibers of regenerated cellulose and mixtures thereof, and these fibers are together contained in the nonwoven in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven, and wherein the nonwoven is in the form of a web, has a longitudinal direction in the running direction of the web, a cross direction orthogonal thereto and lying in the plane of the web and a thickness direction orthogonal to longitudinal direction and the cross direction and is shaped such that the nonwoven has a wave structure in the plane formed by the cross direction and the thickness direction with a wave height of at least 50 µm and at most 1000 µm, as well as a wave length of at least 150 µm and at most 5000 µm.
 2. The filter material as claimed in claim 1, in which the wave height is at least 150 µm and at most 800 µm.
 3. The filter material as claimed in claim 1, in which the wave length is at least 500 µm and at most 2000 µm.
 4. The filter material as claimed in claim 1, in which the amount of pulp fibers, of fibers of regenerated cellulose or of said mixture thereof is at least 60% and at most 95%, each with respect to the mass of the hydro-entangled nonwoven.
 5. The filter material as claimed in claim 1, in which the pulp fibers are sourced from coniferous woods, spruce, pine or fir, deciduous woods, hemp, flax, jute, ramie, kenaf, kapok, coconut, abacá, sisal, cotton or esparto grass or are formed by a mixture of two or more different pulp fibers from these origins. 6-7. (canceled)
 8. The filter material as claimed in claim 1, in which the hydro-entangled nonwoven consists substantially exclusively, but at least to 95% with respect to the mass of the hydro-entangled nonwoven of pulp fibers, fibers of regenerated cellulose or a mixture thereof.
 9. The filter material as claimed in claim 1, in which the hydro-entangled nonwoven of the filter material contains at least 5% and less than 50% staple fibers from cellulose acetate, each with respect to the mass of the hydro-entangled nonwoven.
 10. The filter material as claimed in claim 1, in which the basis weight of the hydro-entangled nonwoven is at least 25 g/m² and at most 150 g/m² .
 11. The filter material as claimed in claim 1, in which the thickness of the hydro-entangled nonwoven is at least 120 µm and at most 800 µm .
 12. The filter material as claimed in claim 1, in which the density of the hydro-entangled nonwoven is at least 80 kg/m³ and at most 220 kg/m³.
 13. The filter material as claimed in claim 1, in which the width-related tensile strength of the hydro-entangled nonwoven is at least 0.07 kN/m and at most 4 kN/m. 14-16. (canceled)
 17. A segment comprising a filter material as claimed in claim 1 and a wrapper material.
 18. (canceled)
 19. The segment as claimed in claim 17, with a length of at least 6 mm and at most 35 mm.
 20. The segment as claimed in claim 17, with a draw resistance in accordance with ISO 6565:2015 of at least 1 mmWG/mm and at most 12 mmWG/mm. 21-23. (canceled)
 24. A smoking article comprising a segment that contains an aerosol-forming material and a segment as claimed in claim
 17. 25. The smoking article as claimed in claim 24, wherein the smoking article is a filter cigarette and the aerosol-forming material is formed by tobacco.
 26. The smoking article as claimed in claim 24, during the intended use of which the aerosol-forming material is just heated but not burnt.
 27. A process for manufacturing a filter material for smoking articles comprising the following steps A to D, A - providing a fiber web comprising fibers, selected from the group consisting of pulp fibers, fibers from regenerated cellulose and mixtures thereof, B - hydro-entangling the fiber web by means of a plurality of water jets directed onto the fiber web, C - generating a wave structure in the nonwoven by means of a plurality of water jets directed onto the fiber web, and D - drying the hydro-entangled nonwoven, wherein the proportion of said fibers in the fiber web in step A is selected such that these fibers are together contained in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven in the dried state from step D, wherein the fiber web provided in step A has a longitudinal direction in the running direction of the fiber web, a cross direction orthogonal thereto lying in the plane of the fiber web and a thickness direction orthogonal to longitudinal direction and cross direction, and the water jets directed onto the fiber web in step C are disposed such that they have a distance from each other in cross direction from center point to center point of the water jets at the location of impact on the fiber web of at least 150 µm and at most 5000 µm and the pressure of each water jet in step C is at least 2 MPa and at most 70 MPa, and the nonwoven obtained in step D has a wave structure in the plane formed by the cross direction and the thickness direction with a wave height of at least 50 µm and at most 1000 µm, as well as a wave length of at least 150 µm and at most 5000 µm.
 28. The process as claimed in claim 27, in which the water jets for carrying out step C are directed onto both sides of the fiber web.
 29. (canceled)
 30. The process as claimed in claim 27, in which the water jets in step C exit from an opening which has an area of at least 450 µm² and at most 50000 µm² and is a circular opening.
 31. The process as claimed in claim 27, in which the pressure of the water jets in step C is at least 3 MPa and at most 40 MPa, wherein the pressure for generating the wave structure is selected as a function of the speed of the fiber web in a manner such that for the ratio p/v of the pressure p in MPa to the speed v of the fiber web in m/s, that the following holds: 2.5 ≤ p/v ≤ 20 .
 32. The process as claimed in claim 27, in which the pressure of the water jets in step B is at least 0.5 MPa and at most 60 MPa, wherein the pressure in step B is selected as a function of the speed of the fiber web such that for the ratio p/v of the pressure p in MPa to the speed v of the fiber web in m/s, that the following holds: 2 ≤ p/v ≤
 20. 33-35. (canceled)
 36. The process as claimed in claim 27, in which in a variation A1 of the process, the fiber web in step A is provided by means of a wet-laid process, which comprises the following sub-steps A1.1 to A1.3: A1.1 - manufacturing an aqueous suspension comprising fibers selected from the group consisting of pulp fibers, fibers from regenerated cellulose and mixtures thereof, in which the amount of fibers is selected such that these fibers are together contained in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven in the dried state from step D, A1.2 - applying the suspension from step A1.1 to a running wire, and A1.3 - de-watering the suspension by means of the running wire in order to form a fiber web, in which the process comprises a further sub-step A1.4: A1.4 - adjusting the moisture content of the fiber web by drying or moistening, wherein the aqueous suspension in step A1.1 has a solid content of at least 0.01% and at most 0.2%, in which the running wire of steps A1.2 and A1.3 is inclined upwards in the running direction of the fiber web from the horizontal by an angle of at least 5° and at most 30°. 37-40. (canceled)
 41. The process as claimed in claim 27, in which in a variation A2 of the process, the fiber web in step A is provided by means of an air-laid process, which comprises the following sub-steps A2.1 and A2.2: A2.1 - manufacturing a fiber web by an air-laid process, wherein the fiber web comprises fibers which are selected from the group consisting of pulp fibers, fibers from regenerated cellulose and mixtures thereof, in which the amount of these fibers is selected in a manner such that these fibers are together contained in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven in the dried state from step D, and A2.2 - moistening the fiber web.
 42. The process as claimed in claim 27, in which the drying in step D is at least partially carried out by through-air drying. 